1. Field of the Invention
This invention relates to embedded system applications for use with electronic circuit breaker systems in which the embedded system applications require at least square root computations. This invention further relates to microcontroller or microprocessor based systems that determine at least square roots using a fractional precision integer square root method to relatively accurately and quickly determine at least the square roots of integer values of various input parameters associated with electronic circuit breaker systems.
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2. Description of Related Art
To determine at least the square root of a number, known embedded system applications may use certain commercially available language compilers, such as C-language compilers that use a floating point square root method having double precision accuracy. For certain embedded systems applications, however, double precision accuracy may not be required. Accordingly, such applications may also use a relatively fast integer method. The accuracy of this method, however, may not be adequate in certain applications.
One example of an embedded system application that requires greater speed than the floating point method and better accuracy than the fast integer method are electronic circuit breaker systems that are capable of measuring various input parameters representing electrical energy usage in approximately real-time, such as are used in the power industry. However, determining the RMS values for current or voltage input parameters or determining at least the square-roots associated with certain harmonics calculations may require a significant portion of the computing time of the processor(s) of the electronic circuit breaker system. Commercially available C-language compilers using floating point methods may take on the order of approximately 10 milliseconds to run on a 16-bit microcontroller or microprocessor running at 16 MHZ.
Accordingly, in electronic circuit breaker system applications, the processor that determines the RMS currents and voltages in approximately real-time to measure energy usage may use on the order of about fifty (50) percent of its computing time to determine square roots using such floating point methods. In particular, electronic circuit breaker systems that measure energy usage may require on the order of about 50 square root calculations every second. If the processor takes 10 milliseconds to determine each square root, then the processor will use on the order of one-half (1/2) second of a one second interval simply to determine the square roots of various measured input parameters. Where energy measurement is done in approximately real-time, this may leave insufficient processing time for other purposes, such as updating displays, reading keypads and handling communications to a remote processor.